src/test/ui/parser/underscore_item_not_const.rs

// Test that various non-const items and associated consts do not permit `_` as a name.

// Associated `const`s:

pub trait A {
    const _: () = (); //~ ERROR expected identifier, found reserved identifier `_`
}
impl A for () {
    const _: () = (); //~ ERROR expected identifier, found reserved identifier `_`
}
impl dyn A {
    const _: () = (); //~ ERROR expected identifier, found reserved identifier `_`
}

// Other kinds of items:

static _: () = (); //~ ERROR expected identifier, found reserved identifier `_`
struct _(); //~ ERROR expected identifier, found reserved identifier `_`
enum _ {} //~ ERROR expected identifier, found reserved identifier `_`
fn _() {} //~ ERROR expected identifier, found reserved identifier `_`
mod _ {} //~ ERROR expected identifier, found reserved identifier `_`
type _ = (); //~ ERROR expected identifier, found reserved identifier `_`
use _; //~ ERROR expected identifier, found reserved identifier `_`
use _ as g; //~ ERROR expected identifier, found reserved identifier `_`
trait _ {} //~ ERROR expected identifier, found reserved identifier `_`
trait _ = Copy; //~ ERROR expected identifier, found reserved identifier `_`
macro_rules! _ { () => {} } //~ ERROR expected identifier, found reserved identifier `_`
union _ { f: u8 } //~ ERROR expected one of `!` or `::`, found reserved identifier `_`

fn main() {}